Milling cutters, in particular face milling cutters, generally comprise a plurality of cutting inserts that are arranged around a periphery of a tool body. Each of the cutting inserts is retained within an insert pocket by suitable retaining means. Typically, the cutting insert is retained by a clamping screw that passes through a through bore of the cutting insert and threadingly engages a threaded bore within the insert pocket.
In order to increase the efficiency and the cost effectiveness of the cutting tool, it is desired to mount as many cutting inserts as possible for a given tool diameter. For that purpose, it is a need to decrease the space between two consecutive cutting inserts.
When the cutting inserts are radially mounted with respect to the axis of rotation of the cutting tool, the space required for the clamping screws is relatively large. On the one hand, the thickness of the tool body behind each cutting insert should be sufficient for locating therein the threaded bore. On the other hand, there should be left considerable space in front of every cutting insert for enabling easy insertion of the clamping screw into the through bore of the cutting insert and for enabling a screwdriver to freely engage the head of the clamping screw without being obstructed by the tool body.
In view of the above, when it is desired to have an extra-fine pitch milling cutter, it is preferable to retain the cutting inserts by means of a wedge-type lock. In such type of locks, the clamping screw is generally radially directed and, therefore, occupies minimal space at the periphery of the milling cutter.
There are several types of wedge lock milling cutters known in the art. In some cases, the clamping screw passes through a through bore in the wedge. In other cases, the clamping screw presses sideways on the wedge. In these types of clamping mechanisms, the cutting insert is retained in its pocket by means of a wedging force acting thereon by the wedge that is tightened by the clamping screw.
These types of clamping mechanisms suffer from a disadvantage that the cutting insert is retained to its pocket solely by a pressure applied thereon by the wedge. In case of a slight untightening of the clamping screw as a result of vibration or negligence, and, with the addition of the outwardly radially directed centrifugal forces acting on the cutting insert as a result of the rotation of the cutting tool, the cutting insert may lose the contact with its pocket walls and fly out during a machining operation.